Sensors have long been used in the art to sense and measure a variety of environmental and/or physical states. Certain sensors, such as capacitive sensors, have been particularly advantageous for having the capability to directly measure a variety of states, such as motion, chemical composition, electric field, etc., and, indirectly, sense many other variables that may be converted into motion or dielectric constants, such as pressure, acceleration, fluid level, fluid composition and the like. Additional applications for capacitive sensors include flow measurement, liquid level, spacing, scanned multiplate sensing, thickness measurement, ice detection, and shaft angle or linear position.
In order to accurately measure low pressures, sensors require fairly large diaphragms to provide the accuracy required. The deflection of these diaphragms is measured to determine the pressure differential on either side of the diaphragm. Unfortunately, these large diaphragms are also sensitive to orientation as gravity can have a significant effect (up to 2% change, or 0.5 Pa on a 25 Pa sensor). For fixed installations, the diaphragms of these sensors are always oriented parallel to the gravity vector, eliminating the need for compensation. For portable applications, however, the orientation cannot be guaranteed, and a method for compensation is required.
The current approach for orientation compensation is to provide 2 sensors, oriented 180° from each other, such that the gravity effects are equal and opposite between the two sensors. The output of the two sensors (PSensor1 and PSensor2) are averaged (Pavg), and the errors introduced by gravity (Eg) are essentially cancelled out:
      P    avg    =                    (                              P                          sensor              ⁢                                                          ⁢              1                                +                      E            g                          )            +              (                              P                          sensor              ⁢                                                          ⁢              2                                -                      E            g                          )              2  One of the biggest problems with this approach is that it requires two relatively expensive sensors in order to provide the orientation independence. The sensing costs are twice that of a single sensor implementation. Additionally, if the sensors are not matched (e.g., in diaphragm thickness and tension), each sensor will have a different error induced by gravity, introducing a resultant error after the averaging, which cannot otherwise be compensated. Thus, by combining two sensors, the inaccuracy components of non-repeatability and hysteresis will become cumulative in the two sensors, causing an overall decrease in the accuracy of the combined sensors over that of each of the individual sensors. Accordingly, improved techniques, systems and methods are needed to provide more accurate readings.